Pat dry the fish.
Drizzle the fish with lemon juice and season with salt and pepper. Place one bay leaf inside each fish.
Peel and finely chop the garlic.
Melt the butter, add the garlic and cook briefly. Remove from the heat and leave to stand for 10 minutes. Place each fish on a buttered sheet of baking paper, then spread the garlic butter over the fish.
Preheat the oven to 200°C (180°C fan, gas 6). Drain the olives and quarter lengthways.
Scatter the olives over the fish.
Wrap the fish tightly into the parchment paper. Fold the ends of the paper several times so that the packets are tightly sealed.
Place the fish packets on a baking tray and bake for 20-25 minutes.
Serve the red mullets in the paper, ready to open at the table.